Power system of electric vehicle, electric vehicle comprising the same and method for heating battery group of electric vehicle

ABSTRACT

A power system of an electric vehicle, an electric vehicle comprising the same and a method for heating a battery group of the electric vehicle are provided. The power system comprises: a battery group; a battery heater, in which the battery heater comprises a output power adjusting module configure to adjust a heating power of the battery heater by adjusting a charge current and/or a discharge current; a battery management device configured to control the output power adjusting module to adjust the heating power of the battery heater to heat the battery group according to a temperature of the battery group when the temperature of the battery group is lower than a first heating threshold and a residual electric quantity of the battery group is larger than a parking electric quantity threshold; a motor controller connected with a motor and an electric distribution box respectively; and an isolation inductor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to, and benefits of Chinese PatentApplication Serial No. 201210160417.5, filed with the State IntellectualProperty Office of P.R.C., on May 22, 2012, the entire contents of whichare incorporated herein by reference.

FIELD OF THE INVENTION

Exemplary embodiments of the present disclosure relate generally to apower system and, more particularly, to a power system of an electricvehicle, an electric vehicle comprising the power system and a methodfor heating a battery group of the electric vehicle.

BACKGROUND

With the development of the science and technology, new energy vehiclesespecially electric vehicles, gradually enter into ordinary families asa means of transportation. The performance requirement, especially thecomfort requirement of a user for the vehicle, is higher and higher,which requires that the vehicle must adapt to different operatingrequirements. But currently most electric vehicles cannot satisfy suchrequirements. Especially in winter, the temperature is low so that thecapability of a battery, no matter the discharge capability or thebattery capacity, may be decreased or the battery cannot even be used.Specifically, the work temperature of the battery especially lithium ionbattery is generally within a range from −20° C. to 55° C., and thebattery is not allowed to be charged at a low temperature. Under a lowtemperature condition, the battery in the electric vehicle may have thefollowing problems. (1) The lithium ions may be deposited easily at thenegative electrode and lose the electrical activity at the lowtemperature, and therefore, if the battery in the electric vehicle isfrequently used at the low temperature, the life of the battery may beshortened and a safety problem may be caused accordingly. (2) When thelithium ion battery is charged at the low temperature, the lithium ionsmay be deposited easily at the negative electrode to become dead ionsand thus the capacity of the battery may be decreased. Moreover, thedeposited ions grow larger and larger during the continuous use, thusleading to a potential danger such as an internal short circuit. (3) Thedischarge capability of the battery is limited at the low temperature.All of the problems listed above may be not favorable for the electricvehicle which uses green and environment friendly new energy.

The method for heating a battery is an important technology in theelectric vehicle field. A heating strategy of the battery and theperformance of the battery heater influence the comfort, operationstability and safety of the vehicle directly. Many new technologies areapplied in the battery heating, but because of the self-capabilitydefects, these technologies are not widely applied in the vehicle field.For example, a thermal insulation sleeve is provided to warm a batteryby thermal insulation material; an infrared radiation film is used toheat the battery and a thermal insulation sleeve is provided to keepwarm; or a heating patch is attached on the surface of the battery.These methods are only suitable for the fixed battery. Furthermore,using the external power to heat the battery is not suitable for thevehicle which is not fixed in position. Therefore, the above methodshave not been widely applied in the electric vehicle field.

BRIEF SUMMARY OF THE DISCLOSURE

According to a first aspect of the present disclosure, a power system ofan electric vehicle is provided. The power system comprises: a batterygroup; a battery heater, connected with the battery group and configuredto charge and discharge the battery group to heat the battery group, inwhich the battery heater comprises an output power adjusting moduleconfigured to adjust a heating power of the battery heater by adjustinga charge current and/or a discharge current; a battery managementdevice, connected with the battery group and the battery heaterrespectively, configured to control the output power adjusting module toadjust the heating power of the battery heater to heat the battery groupaccording to a temperature of the battery group when the temperature ofthe battery group is lower than a first heating threshold and a residualelectric quantity of the battery group is larger than a parking electricquantity threshold; an electric distribution box, configured todistribute a voltage output by the battery group; a motor; a motorcontroller, connected with the motor and the electric distribution boxrespectively, comprising a first input terminal, a second input terminaland a pre-charging capacitor connected between the first input terminaland the second input terminal, and configured to supply power to themotor according to a control command and a voltage distributed by theelectric distribution box; and an isolation inductor, connected betweenthe battery group and the electric distribution box, in which aninductance of the isolation inductor matches with a capacitance of thepre-charging capacitor.

With the power system of the electric vehicle according to embodimentsof the present disclosure, by using a large current discharge of thebattery group in the electric vehicle, the internal resistor of thebattery itself may be heated so that the battery group may be heated.Without any external power supply, the electricity for heating istotally supplied by the battery group. A heating management may beperformed for the battery group by the battery management device and thebattery heater, which may greatly reduce the restriction on the use ofthe electric vehicle at the low temperature, thus satisfying therequirements of running and charging at the low temperature. Moreover,the power system heats the battery group directly, and therefore, ahigher heating efficiency, a lower cost and a better utility may beobtained.

According to a second aspect of the present disclosure, an electricvehicle comprising the above power system is provided. The electricvehicle can normally run in a cold region and the battery group can beheated while the electric vehicle is running, thus ensuring a safe andsmooth running.

According to a third aspect of the present disclosure, a method forheating a battery group of an electric vehicle is provided, comprising:detecting a temperature and a residual electric quantity of the batterygroup; if the temperature of the battery group is lower than a firstheating threshold and the residual electric quantity of the batterygroup is larger than a parking electric quantity threshold, adjusting aheating power of a battery heater to heat the battery group according tothe temperature of the battery group; and if the temperature of thebattery group is lower than the first heating threshold and the residualelectric quantity of the battery group is lower than the parkingelectric quantity threshold, indicating the battery group is inhibitedfrom being heated or charged and the electric vehicle is inhibited frombeing driven.

With the method for heating the battery group of the electric vehicleaccording to embodiments of the present disclosure, the battery groupmay be heated directly without any external power supply. Thetemperature of the battery group may be increased to a requiredtemperature and then the battery group may be charged or dischargednormally, which may greatly reduce the restriction on the use of theelectric vehicle at the low temperature, thus satisfying therequirements of running and charging at the low temperature.Furthermore, by adjusting the heating power of the battery heateraccording to the real-time temperature of the battery group, it ispossible to control the heating procedure more precisely to make betteruse of the performance of the battery group and increase the safety ofthe battery group.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described exemplary embodiments of the present disclosure ingeneral terms, reference will now be made to the accompanying drawings,which are not necessarily drawn to scale.

FIG. 1 illustrates a schematic diagram of a power system of an electricvehicle according to an exemplary embodiment:

FIG. 2 illustrates a schematic diagram of a power system of an electricvehicle according to an exemplary embodiment:

FIG. 3A illustrates an electric principle diagram of a power system ofan electric vehicle according to an exemplary embodiment;

FIG. 3B illustrates an electric principle diagram of a power system ofan electric vehicle according to an exemplary embodiment;

FIG. 4 illustrates an electric connection diagram of a power system ofan electric vehicle according to an exemplary embodiment;

FIG. 5 illustrates an electric connection diagram of a power system ofan electric vehicle according to an exemplary embodiment;

FIG. 6 illustrates a schematic diagram of an electric distribution boxin a power system of an electric vehicle according to an exemplaryembodiment:

FIG. 7 illustrates a flow chart of a method for heating a battery groupof an electric vehicle according to an exemplary embodiment;

FIG. 8 illustrates a flow chart of a method for heating a battery groupof an electric vehicle according to an exemplary embodiment;

FIG. 9 illustrates a flow chart of a method for heating a battery groupof an electric vehicle according to an exemplary embodiment;

FIG. 10 illustrates a flow chart of a method for heating a battery groupof an electric vehicle according to an exemplary embodiment; and

FIG. 11 illustrates a flow chart of a method for heating a battery groupof an electric vehicle according to an exemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings. It is readilyappreciated by those having ordinary skill in the art that the presentlyclaimed subject matter may be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.

In the description, relative terms such as “longitudinal”, “lateral”,“lower”, “upper”, “front”, “rear”, “left”, “right”. “horizontal”,“vertical”, “above”, “below”, “up”, “top”, “bottom” “external”,“internal” as well as derivative thereof (e.g., “horizontally”,“downwardly”, “upwardly”, etc.) should be construed to refer to theorientation as then described or as shown in the drawings underdiscussion. These relative terms are for convenience of description anddo not require that the present disclosure be constructed or operated ina particular orientation.

In the description, terms concerning attachments, coupling and the like,such as “connected” and “interconnected”, refer to a relationship inwhich structures are secured or attached to one another throughmechanical or electrical connection, or directly or indirectly throughintervening structures, unless expressly described otherwise. Specificimplications of the above phraseology and terminology may be understoodby those skilled in the art according to specific situations.

Referring to FIG. 1 and FIG. 2, in some embodiments of the presentdisclosure, a power system of an electric vehicle comprises: a batterygroup 101, a battery heater 102, a battery management device 103, anelectric distribution box 104, a motor 105, a motor controller 106 andan isolation inductor L2. The battery heater 102 is connected with thebattery group 101 and configured to charge and discharge the batterygroup 101 to heat the battery group 101.

Referring to FIG. 3A or FIG. 3B, the battery heater 102 includes anoutput power adjusting module 1021, and the output power adjustingmodule 1021 is configured to adjust a heating power of the batteryheater 102 by adjusting a discharge current and/or a charge current. Thebattery management device 103 is connected with the battery heater 102via a CAN (controller area network) cable 107 and connected with thebattery group 101 via a sampling cable 108 to sample the temperature andvoltage of each battery and the output current of the battery group 101.In addition, the battery management device 103 is also configured tojudge the current status of the electric vehicle, to calculate thetemperature and the residual electric quantity of the battery group 101,and to send the control signals to the relevant electric devices via theCAN cable 107 so as to manage the related devices.

Specifically, the battery management device 103 is configured to controlthe output power adjusting module 1021 to adjust the heating power ofthe battery heater 102 to heat the battery group 101 according to thetemperature of the battery group 101 when the temperature of the batterygroup 101 is lower than a first heating threshold and the residualelectric quantity of the battery group 101 is larger than a parkingelectric quantity threshold. The electric distribution box 104 is a highvoltage device for turning on and off the large current. A voltageoutput by the battery group 101 is distributed by the battery managementdevice 103 by sending a control signal to the electric distribution box104.

The motor controller 106 is connected with the motor 105 and theelectric distribute box 104 respectively, and includes a first inputterminal, a second input terminal and a pre-charging capacitor C2connected between the first input terminal and the second inputterminal. The motor controller 106 is configured to supply power to themotor 105 according to a control command and a voltage distributed tothe motor controller 106 by the electric distribution box 104.Specifically, the motor controller 106 converts the DC supplied by thebattery group 101 into the three-phase AC required by the motor 105 tosupply power to the motor 105 by the internal driving circuit of themotor controller 106, and controls the motor 105 according to thecontrol signal sent by the battery management device 103. The isolationinductor L2 is connected between the battery group 101 and the electricdistribution box 104, and the inductance of the isolation inductor L2matches with the capacitance of the pre-charging capacitor C2.

In one embodiment of the present disclosure, the battery heater 102 maybe configured to perform a failure self-test and send the test result tothe battery management device 103.

Referring to FIGS. 3A and 3B, the battery heater 102 further includes: afirst switch module 301, at least one first capacitor C1, a firstinductor L1 and a second switch module 302. A first terminal of the atleast one first switch module 301 is connected with a first electrode ofthe battery group 101 and the isolation inductor L2 respectively. Afirst terminal of the at least one first capacitor C1 is connected witha second terminal of the first switch module 301 via the output poweradjusting module 1021, and a second terminal of the at least one firstcapacitor C1 is connected with a second electrode of the battery group101.

A first terminal of the first inductor L1 is connected with a nodebetween the first switch module 301 and the at least one first capacitorC1. A first terminal of the second switch module 302 is connected with asecond terminal of the first inductor L1, and a second terminal of thesecond switch module 302 is connected with the second electrode of thebattery group 101. The control terminal of the first switch module 301and the control terminal of the second switch module 302 are connectedwith the battery management device 103.

The battery management device 103 sends a heating signal to the controlterminal 5I of the first switch module 301 and the control terminal ofthe second switch module 302 to control the first switch module 301 andthe second switch module 302 to turn on in turn so as to generate acharge current and a discharge current in turn. When the first switchmodule 301 is on, the second switch module 302 is off, and when thesecond switch module 302 is on, the first switch module 301 is off. Itshould be noted that, in one embodiment, there may be one firstcapacitor C1 or a plurality of first capacitors C1 in the battery heater102. Referring to FIG. 3A-3B, the number of the first capacitors C1 is4. For clarity purpose, the four first capacitors C1 in FIG. 3A aredenoted by C11, C12, C13 and C14 respectively, and the four firstcapacitors C1 in FIG. 3B are denoted by C.1, C.2, C.3 and C.4respectively.

Referring to FIGS. 3A-3B, the ESR is an equivalent resistor of thebattery group 101, the ESL is an equivalent inductor of the batterygroup 101, and E is a battery package. L2 is an isolation inductor andis configured to isolate the battery heating circuit Part 2 from themotor equivalent load circuit Part 5. Therefore, the reversed voltage ofthe battery group 101 is absorbed by the isolation inductor L2 and maynot be applied to the load follow-up. C2 is a pre-charging capacitor;and R is the equivalent load of the motor. D1 and D2 are diodes forforming corresponding charging/discharging loops. When the batteryheater is operational, the internal switch module thereof turns on oroff in a certain timing sequence.

Referring to FIGS. 3A-3B, according to one embodiment of the presentdisclosure, the switch module (e.g., the first switch module 301 or thesecond switch module 302) may be an insulated gate bipolar transistor(IGBT). When the battery heater 102 starts to work, the internalelements of the battery heater, such as inductors, capacitors are in aninitial status and do not store any energy. The operation procedure ofthe battery heater is described below.

When the IGBT1 is on and the IGBT2 is off, the battery package E chargesthe first capacitor C1 by the charging loop “E-ESR-ESL-D1-C1-E”. Afterthe battery package E has charged the first capacitor C1 for a timeperiod, the voltage of the first capacitor C1 is equal to the voltage ofthe battery package E. But because there is an inductive element in thebattery heater, the first capacitor C1 continues being charged so thatthe voltage of the first capacitor C1 is higher than that of the batterypackage. When the charge current is zero, the first capacitor C1 beginsto discharge by the discharging loop “C1-D1-ESL-ESR-E-C1” until thedischarge current is zero.

When the IGBT1 is off and the IGBT2 is on, the first capacitor C1continues discharging by the discharging loop “C1-D2-L1-IGBT2-C1”.Because there is the first inductor L1, the first capacitor C1 continuesto discharge so that the voltage of the first capacitor C1 is lower thanthat of the battery package E. The above process is thus repeated.

Referring to FIG. 3A, as a corresponding first capacitor C1 (C11, C12,C13 or C14) is chosen, the peak voltage of C11, C12, C13 or C14 in adischarging loop (i.e., heating loop) Part 2 changes, and thus the peakvalues of the forward current and the reverse current in the heatingloop also change. Therefore, the heating power of the battery heater isadjusted. In other words, the larger the capacitance is, the larger theheating power is. Furthermore, changing a duty ratio (i.e., pulse width)of the output pulse of the second switch module 302 may achieve anoptimal action time of the forward charging and the reverse charging inthe heating loop.

In one embodiment of the present disclosure, the output power adjustingmodule 1021 is configured to adjust the duty ratios of the output pulsesof the first switch module 301 and the second switch module 302according to an instruction sent by the battery management device 103.The battery management device 103 sends a CAN signal (instruction) tothe output power adjusting module 1021 of the battery heater 102according to the temperature of the battery group 101 (i.e., batterypackage) so as to make the output power adjusting module 1021 connectwith the corresponding first capacitor C1 (e.g., C11, C12, C13 or C14).Meanwhile, according to the corresponding first capacitor C1, the firstswitch module 301 (i.e., IGBT1) and the second switch module 302 (i.e.,IGBT2) is controlled to turn on or turn off with different pulse signalsso as to adjust the duty ratios of the output pulses of the first switchmodule 301 and the second switch module 302, and therefore, the heatingpower of the battery heater is adjusted to be adapted to a requiredpower to be provided by the battery group 101.

Specifically, as the corresponding first capacitor C1 is chosen (forexample, C11, C12, C13 or C14 is chosen), the peak voltage of the firstcapacitor C1 in the discharging loop (i.e., heating loop) Part 2changes, and thus the peak values of the forward current and the reversecurrent in the discharging loop (i.e., heating loop) Part 2 also change.Therefore, the heating power of the battery heater 102 is adjusted.Furthermore, when the corresponding first capacitor C1 (e.g., C11, C12,C13 or C14) is chosen, the timing sequence of turning on and off thefirst switch module 301 (IGBT1) and the second switch module 302 (IGBT2)needs to be changed.

In other words, the pulse widths of the first switch module 301 (IGBT1)and the second switch module 302 (IGBT2) change with the adjustment ofthe first capacitor C1 (i.e., the selection of the first capacitor C11,C12, C13 or C14). Referring to FIG. 3A, in one embodiment, thecapacitance of the first capacitor C11 is lower than the capacitance ofthe first capacitor C12, the capacitance of the first capacitor C12 islower than the capacitance of the first capacitor C13, and thecapacitance of the first capacitor C13 is lower than the capacitance ofthe first capacitor C14. Thus, by using difference capacitors withdifferent capacitances as the first capacitor C1, the heating power ofthe battery heater 102 is adjusted.

Generally, the lower the temperature of the battery group 101 is, thelower the discharging capability of the battery group 101 is, and thelower the voltage of the battery group 101 is, and thus the lower theoutput power is. Therefore, it conforms to the dischargingcharacteristic of the battery to choose different heating powersaccording to the temperature of the battery group 101. Referring to FIG.3A, when the temperature is very low, the capacitor C11 may be chosen tooutput a low power.

Referring to FIG. 3B, in another embodiment of the present disclosure, aplurality of first capacitors C1 (C.1, C.2, C.3 and C.4) may beidentical. The heating power is adjusted by changing the number of thefirst capacitors connected with the output power adjusting module 1021.In other words, when there are a plurality of first capacitors C1 in thebattery heater 102, the output power adjusting module 1021 adjust thenumber of the first capacitors connected with the output power adjustingmodule 1021 according to an instruction sent by the battery managementdevice 103.

Specifically, referring to FIG. 3B, the four capacitors C.1, C.2, C.3and C.4 are connected in parallel. According to the electricalcharacteristics of the capacitors, the equivalent capacitance of twocapacitors connected in parallel is a sum of the capacitances of the twocapacitors. Therefore, provided the capacitances of the four capacitorsC.1. C.2, C.3 and C.4 are the same, it can be obtained that:

C11=C.1;C12=C.1+C.2;C13=C.1+C.2+C.3;C14=C.1+C.2+C.3+C.4.

Therefore, C14=4*C.1; C13=3*C.1; C12=2*C.1; C11=C.1.

By changing the number of capacitors connected with the output poweradjusting module 1021, the capacitance is changed, and thus the heatingpower is changed. In one embodiment, the output power adjusting module1021 may be a relay, as shown in FIG. 3A-3B.

In one embodiment of the present disclosure, the isolation inductor L2may prevent the pre-charging capacitor C2 from charging the firstcapacitor C1 through the first switch module 301 so that the currentwaveform of the first capacitor C1 may be controlled and thus thecharacteristics of the heating circuit may be controlled. Therefore, thecircuit may run normally.

As a result, when the motor 105 and the battery heater 102 operatesimultaneously, the isolation inductor L2 may be needed.

In one embodiment of the present disclosure, the inductance L of theisolation inductor L2 may be determined according to the formulaT=2π√{square root over (LC)}, where T is an equivalent load operationalperiod of the motor 105 and C is the capacitance of the pre-chargingcapacitor C2. The battery heater 102 needs to control the IGBT moduleand switch on/off the first switch module 301 or the second switchmodule 302. Assuming that a switching frequency of the first switchmodule 301 or the second switch module 302 is t, in order to reduce theinfluence of the battery heater 102 on the motor controller 106, it maybe assumed that a period of a circuit comprising the isolation inductorL2 and the pre-charging capacitor C2 is T. In one embodiment, T>10t,thus meeting the design requirements. Therefore, as used herein, theexpression “T is an equivalent load operational period of the motor 105”means that T is the period of the circuit comprising the isolationinductor L2 and the pre-charging capacitor C2.

In one embodiment of the present disclosure, the battery heater 102further includes a power connector configured to connect and fasten apower cable 109 (shown in FIG. 1). The power connector needs to satisfythe requirement of the anti-vortex. When the battery heater 102 isoperational, the frequency of the current is changed very quickly, whichleads to sharp increase in the temperature of the magnetic material inthe power connector, so the magnetic permeability of the power connectorneeds to low. In one embodiment of the present disclosure, the batteryheater 102 further includes a low voltage connector, which is connectedand communicates with an external system. The low voltage connectorincludes a CAN cable 107 configured to connect to the battery managementdevice 103, a self-test signal cable and a failure signal cable.

Referring to FIG. 2 and FIG. 4, in one embodiment of the presentdisclosure, the isolation inductor L2 is disposed in the battery heater102. A fuse 401 is also disposed in the battery heater 102. As shown inFIG. 4, the battery heater 102 includes the isolation inductor L2, thefuse 401 and a power supply for the battery heater 102. The batteryheater 102 further includes four power connectors, in which two powerconnectors are connected to the battery group 101 via the power cable109 and the other two power connectors are connected to the electricdistribution box 104 via the power cable 109. In one embodiment of thepresent disclosure, the power connectors are used in the head end andthe tail end of a high voltage cable.

In one embodiment of the present disclosure, the isolation inductor L2is disposed in the battery heater 102, and when the battery group 101does not need to be heated, the battery heater 102 may be removed, sothat the electric distribution box 104 may be connected directly to thebattery group 101. The electric vehicle does not need any battery heaterin a high temperature area but needs the battery heater in a lowtemperature area. Therefore, if the electric vehicle needs to bemodified to adapt to different areas, the modification may be small,thus greatly reducing the cost.

Referring to FIG. 1 and FIG. 5, in one embodiment of the presentdisclosure, the isolation inductor L2 may be disposed in the electricdistribution box 104. No matter the isolation inductor L2 is disposed inthe battery heater 102 or the electric distribution box 104, theisolation inductor L2 is disposed between the battery group 101 and theelectric distribution box 104.

Referring to FIG. 1, the electric distribution box 104 is not connectedto the battery heater 102 directly. The battery group 101 includes fourpower connectors, in which two power connectors are connected to thebattery heater 102 via two power cables 109 and the other two powerconnectors are connected to the electric distribution box 104 viaanother two power cables 109. In this embodiment, the power system ofthe electric vehicle further includes a relay 501 configured to selectwhether the isolation inductor L2 is connected into the circuit, asshown in FIG. 5. The battery heater 102 is connected in parallel withthe electric distribution box 104. The fuse 401 is mounted in thebattery group 101.

The isolation inductor L2 is disposed in the electric distribution box104 so that the influence on the electric distribution box 104 by thebattery heater 102 may be greatly reduced. Furthermore, when the batteryheater 102 is operational, the isolation inductor L2 may be connectedinto the circuit by the relay 501, and when the battery heater 102 isnot operational, the isolation inductor L2 may be disconnected from thecircuit by the relay 501.

In one embodiment of the present disclosure, as shown in FIG. 1-2 andFIG. 3A-3B, the power system of the electric vehicle further includes acooling assembly 110 configured to cool the first switch module 301 andthe second switch module 302.

In one embodiment of the present disclosure, the cooling assembly 110includes: a wind channel arranged in the battery heater 102; and a fanarranged at one end of the wind channel. The fan is used to dissipateheat for the battery heater 102.

In another embodiment of the present disclosure, the cooling assembly110 includes: a coolant channel arranged in the battery heater 102; acoolant inlet and a coolant outlet arranged in the battery heater 102respectively. The heat dissipation effect and the sealing performance ofthe battery heater may be improved by using the coolant to cool thebattery heater.

Referring to FIG. 6, the electric distribution box 104 includes: aprimary contactor 601 and a pre-charging-contactor 602. The primarycontactor 601 is configured to distribute the voltage output by thebattery group 101 to power consumption equipment, such as the motor 105of the electric vehicle. The pre-charging-contactor 602 is connectedwith the first input terminal 603 or the second input terminal 604 ofthe motor controller 106, and configured to charge the pre-chargingcapacitor C2 under the control of the battery management device 103before the motor controller 106 controls the motor 105 to start.

In one embodiment of the present disclosure, when the residual electricquantity (also named as SOC (state of charge)) of the battery group 101is larger than a running electric quantity threshold, the electricvehicle is allowed to enter in a running heating mode. The runningelectric quantity threshold is larger than the parking electric quantitythreshold.

The running heating mode means that besides the battery group 101 beingheated by the battery heater 102, other high voltage power consumptionequipment of the electric vehicle, such as a motor and an airconditioner, may work simultaneously under a limited power. Accordingly,the parking heating mode means that except the battery group 101 beingheated by the battery heater 102, the other high voltage powerconsumption equipment of the electric vehicle such as the motor and theair conditioner does not work. The running electric quantity thresholdis a first predetermined residual electric quantity of the battery groupwhen the electric vehicle is allowed to enter in the running heatingmode, and the parking electric quantity threshold is a secondpredetermined residual electric quantity of the battery when theelectric vehicle is allowed to enter in the parking heating mode.

Specifically, when any of the following conditions is satisfied, thebattery management device 103 controls the battery heater 102 to heatthe battery group 101 in the running heating mode:

the temperature of the battery group is higher than a first temperaturethreshold and lower than a second temperature threshold, and theresidual electric quantity of the battery group is larger than a firstelectric quantity threshold;

the temperature of the battery group is higher than the secondtemperature threshold and lower than a third temperature threshold, andthe residual electric quantity of the battery group is larger than asecond electric quantity threshold, while the second electric quantitythreshold is lower than the first electric quantity threshold;

the temperature of the battery group is higher than the thirdtemperature threshold and lower than a fourth temperature threshold, andthe residual electric quantity of the battery group is larger than athird electric quantity threshold, while the third electric quantitythreshold is lower than the second electric quantity threshold; and

the temperature of the battery group is higher than the fourthtemperature threshold and lower than a fifth temperature threshold andthe residual electric quantity of the battery group is larger than afourth electric quantity threshold, while the fourth electric quantitythreshold is lower than the third electric quantity threshold.

In one embodiment of the present disclosure, the first temperaturethreshold may be −30° C., the second temperature threshold may be −25°C., the third temperature threshold may be −20 C., the fourthtemperature threshold may be −15° C., the fifth temperature thresholdmay be −10° C., the first electric quantity threshold may be 30% of thetotal electric quantity of the battery group 101, the second electricquantity threshold may be 27.5% of the total electric quantity of thebattery group 101, the third electric quantity threshold may be 25% ofthe total electric quantity of the battery group 101, and the fourthcapacity threshold may be 22.5% of the total electric quantity of thebattery group 101.

According to one embodiment of the present disclosure, the batterymanagement device 103 judges whether the temperature of the batterygroup 101 is higher than a sixth temperature threshold. If yes and theresidual electric quantity of the battery group 101 is larger than afifth electric quantity threshold, the battery management device 103controls the battery heater 102 to heat the battery group 101 in therunning heating mode. If no, the battery management device 103 judgeswhether the temperature of the battery group 101 is higher than aseventh temperature threshold. If yes and the residual electric quantityof the battery group 101 is larger than a sixth electric quantitythreshold, the battery management device 103 controls the battery heater102 to heat the battery group 101 in the running heating mode. If no,the battery management device 103 judges whether the temperature of thebattery group 101 is higher than an eighth temperature threshold. If yesand the residual electric quantity of the battery group 101 is largerthan a seventh electric quantity threshold, the battery managementdevice 103 controls the battery heater 102 to heat the battery group 101in the running heating mode. If no, the battery management device 103judges whether the temperature of the battery group 101 is higher than aninth temperature threshold. If yes and the residual electric quantityof the battery group 101 is larger than an eighth electric quantitythreshold, the battery management device 103 controls the battery heaterto heat the battery group 101 in the running heating mode.

The sixth temperature threshold is higher than the seventh temperaturethreshold, the seventh temperature threshold is higher than the eighthtemperature threshold, and the eighth temperature threshold is higherthan the ninth temperature threshold. The fifth electric quantitythreshold is lower than the sixth capacity threshold, the sixth capacitythreshold is lower than the seventh capacity threshold, and the seventhcapacity threshold is lower than the eighth capacity threshold.

In one embodiment of the present disclosure, the ninth temperaturethreshold may be −30° C., the eighth temperature threshold may be −25°C., the seventh temperature threshold may be −20° C., the sixthtemperature threshold may be −15° C., the eighth electric quantitythreshold may be 30% of the total electric quantity of the battery group101, the seventh electric quantity threshold may be 27.5% of the totalelectric quantity of the battery group 101, the sixth electric quantitythreshold may be 25% of the total electric quantity of the battery group101, and the fifth electric quantity threshold may be 22.5% of the totalelectric quantity of the battery group 101. In one embodiment of thepresent disclosure, when the residual electric quantity of the batterygroup 101 is lower than the running electric quantity threshold andlarger than the parking electric quantity threshold, the electricvehicle is allowed to enter in the parking heating mode.

Specifically, when any of the following conditions is satisfied, thebattery management device 103 controls the battery heater 102 to heatthe battery group 101 in the parking heating mode:

The temperature of the battery group 101 is higher than a tenthtemperature threshold and lower than an eleventh temperature thresholdand the residual electric quantity of the battery group 101 is largerthan a ninth electric quantity threshold;

The temperature of the battery group 101 is higher than the eleventhtemperature threshold and lower than a twelfth temperature threshold andthe residual electric quantity of the battery group 101 is larger than atenth electric quantity threshold, while the tenth electric quantitythreshold is lower than the ninth electric quantity threshold;

The temperature of the battery group 101 is higher than the twelfthtemperature threshold and lower than a thirteenth temperature thresholdand the residual electric quantity of the battery group 101 is largerthan an eleventh electric quantity threshold, while the eleventhelectric quantity threshold is lower than the tenth electric quantitythreshold; and

The temperature of the battery group 101 is higher than the thirteenthtemperature threshold and lower than a fourteenth temperature thresholdand the residual electric quantity of the battery group 101 is largerthan a twelfth electric quantity threshold, while the twelfth electricquantity threshold is lower than the eleventh electric quantitythreshold.

In one embodiment, the tenth temperature threshold may be −30° C., theeleventh temperature threshold may be −25° C., the twelfth temperaturethreshold may be −20° C., the thirteenth temperature threshold may be−15° C., the fourteenth temperature threshold may be −10° C., the ninthelectric quantity threshold may be 20% of the total electric quantity ofthe battery group 101, the tenth electric quantity threshold may be17.5% of the total electric quantity of the battery group 101, theeleventh electric quantity threshold may be 15% of the total electricquantity of the battery group 101, and the twelfth electric quantitythreshold may be 12.5% of the total electric quantity of the batterygroup 101.

According to one embodiment of the present disclosure, the batterymanagement device 103 judges whether the temperature of the batterygroup 101 is higher than a fifteenth temperature threshold. If yes andthe residual electric quantity of the battery group 101 is larger than athirteenth electric quantity threshold, the battery management device103 controls the battery heater 102 to heat the battery group 101 in theparking heating mode. If no, the battery management device 103 judgeswhether the temperature of the battery group 101 is higher than asixteenth temperature threshold. If yes and the residual electricquantity of the battery group 101 is larger than a fourteenth electricquantity threshold, the battery management device 103 controls thebattery heater 102 to heat the battery group 101 in the parking heatingmode. If no, the battery management device 103 judges whether thetemperature of the battery group is higher than a seventeenthtemperature threshold. If yes and the residual electric quantity of thebattery group 101 is larger than a fifteenth electric quantitythreshold, the battery management device 103 controls the battery heater102 to heat the battery group 101 in the parking heating mode. If no,the battery management device 103 judges whether the temperature of thebattery group is higher than an eighteenth temperature threshold. If yesand the residual electric quantity of the battery group 101 is largerthan a sixteenth electric quantity threshold, the battery managementdevice 103 controls the battery heater 102 to heat the battery group 101in the parking heating mode.

The fifteenth temperature threshold is higher than the sixteenthtemperature threshold, the sixteenth temperature threshold is higherthan the seventeenth temperature threshold, and the seventeenthtemperature threshold is higher than the eighteenth temperaturethreshold. The thirteenth electric quantity threshold is lower than thefourteenth electric quantity threshold, the fourteenth electric quantitythreshold is lower than the fifteenth electric quantity threshold, andthe fifteenth electric quantity threshold is lower than the sixteenthelectric quantity threshold.

In one embodiment, the eighteenth temperature threshold may be −30° C.,the seventeenth temperature threshold may be −25° C., the sixteenthtemperature threshold may be −20° C., the fifteenth temperaturethreshold may be −15° C., the sixteenth electric quantity threshold maybe 20% of the total electric quantity of the battery group 101, thefifteenth electric quantity threshold may be 17.5% of the total electricquantity of the battery group 101, the fourteenth electric quantitythreshold may be 15% of the total electric quantity of the battery group101, and the thirteenth electric quantity threshold may be 12.5% of thetotal electric quantity of the battery group 101.

According to some embodiments of the present disclosure, the batterymanagement device 103 may control the battery heater 102 to heat thebattery group 101 in the running heating mode or in the parking heatingmode according to the temperature and residual electric quantity of thebattery group 101. The control accuracy of the battery management device103 is higher and it is easier to achieve the control procedure.

In one embodiment of the present disclosure, the power system furthercomprises a heating button connected with the battery management device103. When the heating button is pressed, the battery management device103 sends a heating signal to the battery heater 102 to control thebattery heater 102 to heat the battery group 101. The battery managementdevice 103 is further configured to: after controlling the batteryheater 102 to heat the battery group 101, if the heating button ispressed again, judge whether the operation of pressing the buttonsatisfies a preset condition (i.e., judge whether the heating button ispressed and held for a preset time). If yes, control the electricvehicle and/or the battery heater 102 according to the temperature andthe residual electric quantity of the battery group 101.

Specifically, if the temperature of the battery group 101 is lower thana nineteenth temperature threshold, the battery management device 103indicates to inhibit the electric vehicle from being heated, driven orcharged; and if the temperature of the battery group 101 is higher thanthe nineteenth temperature threshold, the battery management device 103further judges whether the residual electric quantity of the batterygroup 101 is larger than a seventeenth electric quantity threshold.

Specifically, if the residual electric quantity of the battery group 101is lower than the seventeenth electric quantity threshold and thetemperature of the battery group 101 is higher than the nineteenthtemperature threshold, the battery management device 103 indicates toinhibit the electric vehicle from being heated, driven or charged; andif the residual electric quantity of the battery group 101 is largerthan the seventeenth electric quantity threshold and the temperature ofthe battery group 101 is higher than the nineteenth temperaturethreshold, the battery management device 103 allows the electric vehicleto run under a limited power.

In one embodiment of the present disclosure, the nineteenth temperaturethreshold may be −20° C., and the seventeenth electric quantitythreshold may be 25% of the total electric quantity of the battery group101.

In one embodiment of the present disclosure, the battery managementdevice 103 is further configured to adjust the output power of thebattery heater 102 according to the real time temperature of the batterygroup 101 to heat the battery group 101 by different heating procedures.Specifically, when the temperature of the battery group 101 is higherthan a third heating threshold and lower than a fourth heatingthreshold, the battery management device 103 controls the battery heater102 to heat the battery group 101 with a first power.

When the temperature of the battery group 101 is higher than a fourthheating threshold and lower than a fifth heating threshold, the batterymanagement device 103 controls the battery heater 102 to heat thebattery group 101 with a second power, in which the second power islower than the first power. When the temperature of the battery group101 is higher than a fifth heating threshold and lower than a sixthheating threshold, the battery management device 103 controls thebattery heater 102 to heat the battery group 101 with a third power, inwhich the third power is lower the second power; or when the temperatureof the battery group 101 is higher than a sixth heating threshold andlower than a seventh heating threshold, the battery management device103 controls the battery heater 102 to heat the battery group 101 with afourth power, in which the fourth power is lower than the third power.

In one embodiment of the present disclosure, the third heating thresholdmay be −30° C., the fourth heating threshold may be −25° C., the fifthheating threshold may be −20° C., the sixth heating threshold may be−15° C., and the seventh heating threshold may be −10° C.

In one embodiment of the present disclosure, the battery managementdevice 103 is further configured to judge whether the heating timereaches a first preset time T1 and to control the battery heater 102 tosuspend heating the battery group 101 when the heating time reaches thefirst preset time period. In one embodiment of the present disclosure,after controlling the battery heater 102 to suspend heating the batterygroup 101, the battery management device 103 is further configured tocalculate a suspension time and control the battery heater 102 to heatthe battery group 101 when the suspension time reaches a second presettime period T2.

With the power system of the electric vehicle of the present disclosure,by using the battery group to discharge with large current and by theheating of the internal resistor of the battery group, the battery groupmay be heated. Without any external power supply, the electricity forheating is totally provided by the battery group. A heating managementmay be performed for the battery group by the battery management deviceand the battery heater, which may greatly reduce the restriction on theuse of the electric vehicle at the low temperature and satisfy therequirement of running and charging at the low temperature. That is, thebattery group may be heated while the electric vehicle may run in thelimited power. Moreover, the power system of the electric vehicle heatsthe battery group directly, and therefore, a higher heating efficiency,a lower cost and a better utility may be achieved.

In one embodiment of the present disclosure, an electric vehicle isprovided. The electric vehicle comprises the power system of theelectric vehicle mentioned above. The electric vehicle may run in a lowtemperature environment, and the electric vehicle may run while thebattery group may be heated, thus ensuring a safe and smooth running.

In the following, a method for heating a battery group of an electricvehicle is described in detail with reference to FIG. 7-11. In FIG.7-11, the detailed values (such as, −10° C.) are only illustrative toexplain various thresholds (such as the first heating threshold), butnot used to limit the scope of the present disclosure. The values ofvarious thresholds may be changed according to actual conditions, whichis obvious for a person skilled in the art. Furthermore, the executingorders of the steps in FIG. 7-11 are only illustrative and exemplary,but not used to limit the scope of the present disclosure. The executingorder of the steps may be changed according to actual conditions, whichis also obvious for a person skilled in the art.

Referring to FIG. 11, a method for heating a battery group of anelectric vehicle is provided. The method comprises the following steps.

At step S1101, a temperature and a residual electric quantity of thebattery group are detected.

At step S1102, if the temperature of the battery group is lower than afirst heating threshold and the residual electric quantity of thebattery group is larger than a parking electric quantity threshold, aheating power of a battery heater is adjusted to heat the battery groupaccording to the temperature of the battery group.

At step S1103, if the temperature of the battery group is lower than thefirst heating threshold and the residual electric quantity of thebattery group is lower than the parking electric quantity threshold, thebattery group is inhibited from being heated or charged and the electricvehicle is inhibited from being driven.

According to an embodiment of the present disclosure, referring to FIG.7, specifically, the method for heating the battery group of theelectric vehicle may comprise the following steps.

At step S701, the electric vehicle is powered on.

At step S702, it is detected whether the temperature of the batterygroup is lower than the first heating threshold. If no, step S703 isfollowed; if yes, the electric quantity of the battery group needs to bedetected and then step S704 is followed.

At step S703, the battery management device controls the primarycontactor in the electric distribution box to be switched on. Beforeswitching on the primary contactor, the battery management devicecontrols the pre-charging-contactor to be switched on, and after thepre-charging is finished, the primary contactor is switched on.

At step S704, the battery management device judges whether the heatingand running condition is satisfied according to the temperature and theresidual electric quantity of the battery group. Specifically, when theresidual electric quantity of the battery group is larger than therunning electric quantity threshold, the electric vehicle is allowed toenter in the running heating mode; and when the residual electricquantity of the battery group is lower than the running electricquantity threshold but larger than the parking electric quantitythreshold, the electric vehicle is allowed to enter in the parkingheating mode. The running electric quantity threshold is larger than theparking electric quantity threshold.

At step S705, it is judged whether the heating is in the running heatingmode. If yes, step S706 is followed, and if no, step S707 is followed.

At step S706, when the temperature of the battery group is lower thanthe first temperature threshold, the battery management device sends amessage to a meter to display that the temperature of the battery groupis too low so that the electric vehicle is not allowed to be heated,driven or charged.

When the temperature of the battery group is higher than the firsttemperature threshold and lower than the second temperature threshold,if the residual electric quantity of the battery group is larger thanthe first electric quantity threshold, the battery management devicecontrols the battery heater to heat the battery group, and step S710 isfollowed; and if the residual electric quantity of the battery group islower than the first electric quantity threshold, step S709 is followed.

When the temperature of the battery group is larger than the secondtemperature threshold and lower than the third temperature threshold, ifthe residual electric quantity of the battery group is larger than thesecond electric quantity threshold, the battery management devicecontrols the battery heater to heat the battery group, and step S710 isfollowed; and if the residual electric quantity of the battery group islower than the second electric quantity threshold, step S709 isfollowed, in which the second electric quantity threshold is lower thanthe first electric quantity threshold.

When the temperature of the battery group is higher than the thirdtemperature threshold and lower than the fourth temperature threshold,if the residual electric quantity of the battery group is larger thanthe third electric quantity threshold, the battery management devicecontrols the battery heater to heat the battery group, and step S710 isfollowed; and if the residual electric quantity of the battery group islower than the third electric quantity threshold, step S709 is followed,in which the third electric quantity threshold is lower than the secondelectric quantity threshold.

When the temperature of the battery group is higher than the fourthtemperature threshold and lower than the fifth temperature threshold, ifthe residual electric quantity of the battery group is larger than thefourth electric quantity threshold, the battery management devicecontrols the battery heater to heat the battery group, and step S710 isfollowed; and if the residual electric quantity of the battery group islower than the fourth electric quantity threshold, step S709 isfollowed, in which the fourth electric quantity threshold is lower thanthe third electric quantity threshold.

At step S707, the battery heater heats the battery group in the parkingheating mode.

At step S708, when the temperature of the battery group is lower thanthe tenth temperature threshold, the battery management device sends amessage to the meter to display that the temperature of the batterygroup is too low so that the electric vehicle is not allowed to beheated, driven or charged.

When the temperature of the battery group is higher than the tenthtemperature threshold and lower than the eleventh temperature threshold,if the residual electric quantity of the battery group is larger thanthe ninth electric quantity threshold, the battery management devicecontrols the battery heater to heat the battery group, and step S710 isfollowed; and if the residual electric quantity of the battery group islower than the ninth electric quantity threshold, step S709 is followed.

When the temperature of the battery group is higher than the eleventhtemperature threshold and lower than the twelfth temperature threshold,if the residual electric quantity of the battery group is larger thanthe tenth electric quantity threshold, the battery management devicecontrols the battery heater to heat the battery group, and step S710 isfollowed; and if the residual electric quantity of the battery group islower than the tenth electric quantity threshold, step S709 is followed,in which the tenth electric quantity threshold is lower than the ninthelectric quantity threshold.

When the temperature of the battery group is higher than the twelfthtemperature threshold and lower than the thirteenth temperaturethreshold, if the residual electric quantity of the battery group islarger than the eleventh electric quantity threshold, the batterymanagement device controls the battery heater to heat the battery group,and step S710 is followed; and if the residual electric quantity of thebattery group is lower than the eleventh electric quantity threshold,step S709 is followed, in which the eleventh electric quantity thresholdis lower than the tenth electric quantity threshold.

When the temperature of the battery group is higher than the thirteenthtemperature threshold and lower than the fourteenth temperaturethreshold, if the residual electric quantity of the battery group islarger than the twelfth electric quantity threshold, the batterymanagement device controls the battery heater to heat the battery group,and step S710 is followed; and if the residual electric quantity of thebattery group is lower than the twelfth electric quantity threshold,step S709 is followed, in which the twelfth electric quantity thresholdis lower than the eleventh electric quantity threshold.

At step S709, the battery management device sends a message to the meterto display that the residual electric quantity of the battery group istoo low so that the electric vehicle is not allowed to be heated, drivenor charged.

At step S710, the battery heater performs a self-test to detect whetherthere is a failure. If yes, step S712 is followed; and if no, step S711is followed.

At step S711, the battery heater heats the battery group, and during theheating process, step S713 is also performed.

At step S712, the electric vehicle is not allowed to be heated, drivenor charged.

At step S713, the battery heater performs a self-test to detect whetherthere is a failure. If yes, step S715 is followed; and if no, step S714is followed.

At step S714, it is judged whether the heating is finished. If yes, stepS716 is followed; and if no, step S711 is followed.

At step S715, the battery heater stops heating the battery group.

At step S716, a CAN message is sent to the battery heater to make thebattery heater stop heating the battery group.

In one embodiment of the present disclosure, referring to FIG. 7, thefirst heating threshold may be −10° C., the first temperature thresholdmay be −30° C., the second temperature threshold may be −25° C., thethird temperature threshold may be −20° C., the fourth temperaturethreshold may be −15° C., the fifth temperature threshold may be −10° C.the first electric quantity threshold may be 30% of the total electricquantity of the battery group, the second electric quantity thresholdmay be 27.5% of the total electric quantity of the battery group, thethird electric quantity threshold may be 25% of the total electricquantity of the battery group, the fourth electric quantity thresholdmay be 22.5% of the total electric quantity of the battery group, thetenth temperature threshold may be −30° C., the eleventh temperaturethreshold may be −25° C., the twelfth temperature threshold may be −20°C., the thirteenth temperature threshold may be −15° C., the fourteenthtemperature threshold may be −10° C., the ninth electric quantitythreshold may be 20% of the total electric quantity of the batterygroup, the tenth electric quantity threshold may be 17.5% of the totalelectric quantity of the battery group, the eleventh electric quantitythreshold may be 15% of the total electric quantity of the batterygroup, and the twelfth electric quantity threshold may be 12.5% of thetotal electric quantity of the battery group.

According to an embodiment of the present disclosure, referring to FIG.8, specifically, the method for heating the battery group of theelectric vehicle may comprise the following steps.

At step S801, the electric vehicle is powered on.

At step S802, it is detected whether the temperature of the batterygroup is lower than the first heating threshold. If no, step S803 isfollowed; if yes, the electric quantity of the battery group needs to bedetected and then step S804 is followed.

At step S803, the battery management device controls the primarycontactor in the electric distribution box to be switched on. Beforeswitching on the primary contactor, the battery management devicecontrols the pre-charging-contactor to be switched on, and after thepre-charging is finished, the primary contactor is switched on.

At step S804, the battery management device judges whether the heatingand running condition is satisfied according to the temperature and theresidual electric quantity of the battery group. Specifically, when theresidual electric quantity of the battery group is larger than therunning electric quantity threshold, the electric vehicle is allowed toenter in the running heating mode, and when the residual electricquantity of the battery group is lower than the running electricquantity threshold but larger than the parking electric quantitythreshold, the electric vehicle is allowed to enter in the parkingheating mode. The running electric quantity threshold is larger than theparking electric quantity threshold.

At step S805, it is judged whether the healing is in the running heatingmode. If yes, step S806 is followed, and if no, step S807 is followed.

At step S806, the battery management device judges whether thetemperature of the battery group is higher than the sixth temperaturethreshold. If yes and if the residual electric quantity of the batterygroup is larger than the fifth electric quantity threshold, step S810 isfollowed, and if the residual electric quantity of the battery group islower than the fifth electric quantity threshold, step S809 is followed.If no, the battery management device further judges whether thetemperature of the battery group is larger than the seventh temperaturethreshold.

If yes and the residual electric quantity of the battery group is largerthan the sixth electric quantity threshold, step S810 is followed, andif the residual electric quantity of the battery group is lower than thesixth electric quantity threshold, step S809 is followed. If no, thebattery management device further judges whether the temperature of thebattery group is higher than the eighth temperature threshold.

If yes and the residual electric quantity of the battery group is largerthan the seventh electric quantity threshold, step S810 is followed, andif the residual electric quantity of the battery group is lower than theseventh electric quantity threshold, step S809 is followed. If no, thebattery management device judges whether the temperature of the batterygroup is larger than the ninth temperature threshold.

If yes and the residual electric quantity of the battery group is largerthan the eighth electric quantity threshold, step S810 is followed, andif the residual electric quantity of the battery group is lower than theeighth electric quantity threshold, step S809 is followed. If no, thebattery management device sends a message to the meter to display thatthe temperature of the battery group is too low so that the electricvehicle is not allowed to be heated, driven or charged.

The sixth temperature threshold is higher than the seventh temperaturethreshold, the seventh temperature threshold is higher than the eighthtemperature threshold, and the eighth temperature threshold is higherthan the ninth temperature threshold. The fifth electric quantitythreshold is lower than the sixth electric quantity threshold, the sixthelectric quantity threshold is lower than the seventh electric quantitythreshold, and the seventh electric quantity threshold is lower than theeighth electric quantity threshold.

At step S807, the battery heater heats the battery group in the parkingheating mode.

At step S808, the battery management device judges whether thetemperature of the battery group is higher than the fifteenthtemperature threshold. If yes and the residual electric quantity of thebattery group is larger than the thirteenth electric quantity threshold,step S810 is followed, and if the residual electric quantity of thebattery group is lower than the thirteenth electric quantity threshold,step S809 is followed. If no, the battery management device furtherjudges whether the temperature of the battery group is higher than thesixteenth temperature threshold.

If yes and the residual electric quantity of the battery group is largerthan the fourteenth electric quantity threshold, step S810 is followed,and if the residual electric quantity of the battery group is lower thana fourteenth electric quantity threshold, step S809 is followed. If no,the battery management device further judges whether the temperature ofthe battery group is higher than the seventeenth temperature threshold.

If yes and the residual electric quantity of the battery group is largerthan the fifteenth electric quantity threshold, step S810 is followed,and if the residual electric quantity of the battery group is lower thanthe fifteenth electric quantity threshold, step S809 is followed. If no,the battery management device further judges whether the temperature ofthe battery group is higher than the eighteenth temperature threshold.

If yes and the residual electric quantity of the battery group is largerthan the sixteenth electric quantity threshold, step S810 is followed,and if the residual electric quantity of the battery group is lower thanthe sixteenth electric quantity threshold, step S809 is followed. If no,the battery management device sends a message to the meter to displaythat the temperature of the battery group is too low so that theelectric vehicle is not allowed to be heated, driven or charged.

The fifteenth temperature threshold is larger than the sixteenthtemperature threshold, the sixteenth temperature threshold is largerthan the seventeenth temperature threshold, and the seventeenthtemperature threshold is larger than the eighteenth temperaturethreshold. The thirteenth electric quantity threshold is lower than thefourteenth electric quantity threshold, the fourteenth electric quantitythreshold is lower than the fifteenth electric quantity threshold, andthe fifteenth electric quantity threshold is lower than the sixteenthelectric quantity threshold.

At step S809, the battery management device sends a message to the meterto display that the residual electric quantity of the battery group istoo low so that the electric vehicle is not allowed to be heated, drivenor charged.

At step S810, before heating, the battery heater performs a self-test todetect whether there is a failure. If yes, step S812 is followed, and ifno, step S811 is followed.

At step S811, the battery heater heats the battery group, and during theheating process, step S813 is also performed.

At step S812, the electric vehicle is not allowed to be heated, drivenor charged.

At step S813, the battery heater performs a self-test to detect whetherthere is a failure. If yes, step S815 is followed, and if no, step S814is followed.

At step S814, it is judged whether the heating is finished. If yes, stepS816 is followed, and if no, step S811 is followed.

At step S815, the battery heater stops heating the battery group.

At step S816, a CAN message is sent to the battery heater to make thebattery heater stop heating the battery group.

In one embodiment, referring to FIG. 8, the first heating temperaturethreshold may be −10° C., the ninth temperature threshold may be −30°C., the eighth temperature threshold may be −25° C., the seventhtemperature threshold may be −20° C., the sixth temperature thresholdmay be −15° C., the eighth electric quantity threshold may be 30% of thetotal electric quantity of the battery group, the seventh electricquantity threshold may be 27.5% of the total electric quantity of thebattery group, and the sixth electric quantity threshold may be 25% ofthe total electric quantity of the battery group, the fifth electricquantity threshold may be 22.5% of the total electric quantity of thebattery group, the eighteenth temperature threshold may be −30° C., theseventeenth temperature threshold may be −25° C., the sixteenthtemperature threshold may be −20° C., the fifteenth temperaturethreshold may be −15° C., the sixteenth electric quantity threshold maybe 20% of the total electric quantity of the battery group, thefifteenth electric quantity threshold may be 17.5% of the total electricquantity of the battery group, and the fourteenth electric quantitythreshold may be 15% of the total electric quantity of the batterygroup, and the thirteenth electric quantity threshold may be 12.5% ofthe total electric quantity of the battery group.

According to an embodiment of the present disclosure, referring to FIG.9, the method for heating the battery group of the electric vehicle maycomprise the following steps.

At step S901, the electric vehicle is powered on.

At step S902, the temperature and the residual electric quantity of thebattery group are detected.

At step S903, it is judged whether the temperature of the battery groupis lower than the first heating threshold, if yes, step S905 isfollowed, and if no, step S904 is followed.

At step S904, the battery management device controls thepre-charging-contactor to be switched on, and after the pre-charging isfinished, the primary contactor is switched on. The electric vehicleruns normally. Specifically, the battery management device controls thepre-charging-contactor in the electric distribution box to be switchedon to charge the pre-charging-capacitor and controls thepre-charging-contactor to be switched off after the pre-charging isfinished.

At step S905, the battery management device calculates whether theresidual electric quantity of the battery group is larger than therunning electric quantity threshold. If yes, step S907 is followed, andif no, step S906 is followed.

At step S906, the battery management device calculates whether theresidual electric quantity of the battery group is larger than theparking electric quantity threshold, if yes, step S907 is followed, andif no, step S908 is followed. The running electric quantity threshold islarger than the parking electric quantity threshold.

At step S907, a user confirms whether the battery group needs to beheated, if yes, step S909 is followed, and if no, step S910 is followed.

At step S908, the battery management device sends a message to the meterto display that the residual electric quantity of the battery group istoo low so that the electric vehicle is not allowed to be heated, drivenor charged.

At step S909, the battery heater performs a self-test to detect whetherthere is a failure. If yes, step S91 is followed, and if no, step S912is followed.

At step S910, the battery management device sends a message to the meterto display that the electric vehicle is not allowed to be heated, drivenor charged.

At step S911, the battery management device stops supplying power andsending a message to the battery heater, and sends a message to themeter to display that there is a failure in the battery heater so thatthe electric vehicle is not allowed to be heated, driven or charged.

At step S912, the battery management device sends a heating signal tothe battery heater to heat the battery group.

At step S913, the battery management device controls thepre-charging-contactor to be switched on, and after the pre-charging isfinished, the primary contactor is switched on and then the batterygroup is heated, while the battery heater keeps on performing aself-test. Specifically, the battery management device calculates thecurrent temperature and the current residual electric quantity of thebattery group, calculates the maximum output power of the battery groupaccording to the current temperature and the current residual electricquantity of the battery group, and controls the electric vehicle to rununder a limited power according to the maximum output power.

At step S914, it is judged whether the heating button is pressed andheld for a preset time. If yes, step S915 is followed, and if no, stepS920 is followed. In this embodiment, the preset time may be 2 seconds.

At step S915, it is judged whether the temperature of the battery groupis lower than the nineteenth temperature threshold. If yes, step S916 isfollowed, and if no, step S917 is followed.

At step S916, the electric vehicle is not allowed to be heated, drivenor charged.

At step S917, it is judged whether the residual electric quantity of thebattery group is larger than the seventeenth electric quantitythreshold. If yes, step S918 is followed, and if no, step S919 isfollowed.

At step S918, the electric vehicle is allowed to run under a limitedpower.

At step S919, the battery management device sends a message to the meterto prompt that the user stops heating so that the electric vehicle isnot allowed to be heated, driven or charged.

At step S920, it is detected whether there is a failure in the batteryheater. If yes, step S921 is followed, and if no, step S922 is followed.

At step S921, the battery heater stops working and the meter displays analarm so that the electric vehicle is not allowed to be heated, drivenor charged.

At step S922, it is detected whether the temperature of the batterygroup is higher than the first heating threshold. If yes, step S925 isfollowed, and if no, step S923 is followed.

At step S923, it is detected whether the temperature of any singlebattery in the battery group is higher than the second heatingthreshold. If yes, step S925 is followed, and if no, step S924 isfollowed.

At step S924, it is detected whether the continuous heating time ishigher than a heating time threshold. If yes, step S925 is followed, andif no, step S913 is followed.

At step S925, the heating is finished and the battery heater stopsoperating.

In one embodiment of the present disclosure, the first heating thresholdmay be −10° C., the second heating threshold may be 20° C., thenineteenth temperature threshold may be −20° C., the seventeenthelectric quantity threshold may be 25% of the total electric quantity ofthe battery group, and the heating time threshold may be 20 minutes.

According to an embodiment of the present disclosure, referring to FIG.10, the method for heating the battery group of the electric vehicle maycomprise the following steps.

At step S1001, the electric vehicle is powered on.

At step S1002, the temperature and the residual electric quantity of thebattery group are detected.

At step S1003, it is judged whether the temperature of the battery groupis lower than the first heating threshold. If yes, step S1005 isfollowed, and if no, step S1004 is followed.

At step S1004, the battery management device controls thepre-charging-contactor to be switched on, and after the pre-charging isfinished, the primary contactor is switched on. The electric vehicleruns normally.

At step S1005, the battery management device calculates whether theresidual electric quantity of the battery group is larger than therunning electric quantity threshold. If yes, step S1008 is followed, andif no, step S1006 is followed.

At step S1006, the battery management device calculates whether theresidual electric quantity of the battery group is larger than theparking electric quantity threshold. If yes, step S1008 is followed, andif no, step S1007 is followed. The running electric quantity thresholdis larger than the parking electric quantity threshold.

At step S1007, the battery management device sends a message to themeter to display that the residual electric quantity of the batterygroup is too low so that the electric vehicle is not allowed to beheated, driven or charged.

At step S1008, the user confirms whether the battery group needs to beheated. If yes, step S1009 is followed, and if no, step S1010 isfollowed.

At step S1009, the battery heater performs a self-test to detect whetherthere is a failure, if yes, step S1011 is followed, and if no, stepS1012 is followed.

At step S1010, the battery management device sends a message to themeter to display that the electric vehicle is not allowed to be heated,driven or charged.

At step S1011, the battery management device stops supplying power andsending a message to the battery heater, and sends a message to themeter to display that there is a failure in the battery heater so thatthe electric vehicle is not allowed to be heated, driven or charged.

At step S1012, the battery management device sends a heating signal tothe battery heater to heat the battery group.

At step S1013, the battery management device controls thepre-charging-contactor to be switched on, and after the pre-charging isfinished, the primary contactor is switched on and then the batterygroup is heated, while the battery heater keeps on performing aself-test. Specifically, the battery management device calculates thecurrent temperature and the current residual electric quantity of thebattery group, calculates the maximum output power of the battery groupaccording to the current temperature and the current residual electricquantity of the battery group, and controls the electric vehicle to rununder a limited power according to the maximum output power.

At step S1014, the temperature of the battery group is detected.

At step S1015, when the temperature of the battery group is higher thanthe third heating threshold and lower than the fourth heating threshold,the battery management device controls the battery heater to heat thebattery group with the first power. When the temperature of the batterygroup is higher than the fourth heating threshold and lower than thefifth heating threshold, the battery management device controls thebattery heater to heat the battery group with the second power, in whichthe second power is lower than the first power.

When the temperature of the battery group is higher than the fifthheating threshold and lower than the sixth heating threshold, thebattery management device controls the battery heater to heat thebattery group with the third power, in which the third power is lowerthan the second power; or when the temperature of the battery group ishigher than the sixth heating threshold and lower than the seventhheating threshold, the battery management device controls the batteryheater to heat the battery group with the fourth power, in which thefourth power is lower than the third power.

At step S1016, the battery management device judges whether the heatingtime reaches the first preset time period T1. If yes, step S1017 isfollowed, and if no, step S1018 is followed.

At step S1017, the battery heater suspends working and the batterymanagement device judges whether the suspension time reaches a secondpreset time period T2. If yes, step S1016 is followed, and if no, stepS1017 is followed.

At step S1018, it is judged whether the heating button is pressed andheld for a preset time period. If yes, step S1019 is followed, and ifno, step S1020 is followed. In one embodiment, the preset time periodmay be 2 seconds.

At step S1019, the battery management device sends a message to themeter to prompt that the user stops heating so that the electric vehicleis not allowed to be heated, driven or charged.

At step S1020, it is detected whether there is a failure in the batteryheater. If yes, step S1021 is followed, and if no, step S1022 isfollowed.

At step S1021, the battery heater stops working and the meter displaysan alarm so that the electric vehicle is not allowed to be heated,driven or charged.

At step S1022, it is detected whether the temperature of the batterygroup is higher than the first heating threshold. If yes, step S1025 isfollowed, and if no, step S1023 is followed.

At step S1023, it is detected whether the temperature of any singlebattery in the battery group is higher than the second heatingthreshold. If yes, step S1025 is followed, and if no, step S1024 isfollowed.

At step S1024, it is detected whether the continuous heating time islarger than the heating time threshold. If yes, step S1025 is followed,and if no, step S1013 is followed.

At step S1025, the heating is finished and the battery heater stopsoperating.

In one embodiment of the present disclosure, the third heating thresholdmay be −30° C., the fourth heating threshold may be −25° C., the fifthheating threshold may be −20° C., the sixth heating threshold may be−15° C., the seventh heating threshold may be −10° C., the first heatingthreshold may be −10° C., the second heating threshold may be 20° C.,and the heating time threshold may be 20 minutes.

In some embodiments, when the electric vehicle is powered on, thebattery management device detects the temperature of the battery groupand the status of the primary contactor. The temperature of the batterygroup is an average of temperatures of all single batteries in thebattery group. The battery management device samples the temperature ofeach single battery in the battery group through an informationcollector and calculates the temperature of the battery group.

If the temperature of the battery group is lower than the first heatingtemperature and the residual electric quantity of the battery group islarger than the parking electric quantity threshold, the user pressesand holds the heating button for 2 seconds, and then the batterymanagement device sends a message to the battery heater through the CANcable to allow the battery group to be heated. Before heating thebattery group in the running heating mode, that is, before the motorworks, the battery management device sends the control signal to theelectric distribution box to control the pre-charging-contactor to beswitched on so that the battery group charges the pre-charging capacitorC2. When the voltage of the pre-charging capacitor C2 is substantiallyequal to that of the battery group, the motor is allowed to work.

In one embodiment of the present disclosure, the heating button isdisposed on the meter. Provided that the temperature of the batterygroup is lower than the first heating threshold and the residualelectric quantity of the battery group is larger than the parkingelectric quantity threshold, when the heating button is pressed, thebattery heater is allowed to work. If the heating button is pressedagain and held for 2 seconds, the battery heater is forced to stopoperating.

The primary contactor is disposed in the electric distribution box andconfigured to connect the motor controller to a power supply ordisconnect the motor controller from a power supply. When the residualelectric quantity of the battery group is larger than the runningelectric quantity threshold, the battery management device sends thecontrol signal to the electric distribution box to control the primarycontactor to be switched on so that the motor is allowed to work. Themotor controller converts the DC to the three-phase AC required by themotor through the driving circuit, to supply power to the motor and toallow the electric vehicle to run under a limited power.

The pre-charging-contactor is also disposed in the electric distributionbox and connected to the pre-charging capacitor C2 in series. Inparticular, the pre-charging capacitor C2 is charged before the motorworks. The reasons may be as follows.

In one aspect, an electrical current shock may be avoided in thepre-charging procedure and an agglomeration caused when the primarycontactor is switched on may be avoided. A current limiting resistor isconnected in series between the pre-charging capacitor and thepre-charging-contactor. When the pre-charging is finished, the batterymanagement device controls the primary contactor to be switched on andthen controls the pre-charging-contactor to be switched off.

In another aspect, since the current is larger at the start moment ofthe motor, the voltage of the whole battery group is reduced. Therefore,the pre-charging capacitor C2 is charged firstly until the voltagethereof is substantially equal to that of the battery group, and thenthe motor is started. Because the voltage of the pre-charging capacitorcannot change suddenly, by connecting the pre-charging capacitor and themotor in parallel, the impact on the voltage of the battery groupresulting from the start of the motor may be decreased.

When the battery heater receives the heating signal sent by the batterymanagement device, the battery heater performs a self-test to detectwhether there is a failure in the battery heater. In one embodiment ofthe present disclosure, the battery heater sends a single pulse of 0.5ms to detect whether there is a failure in the battery heater. If thereis not any failure, the battery heater sends a control pulse (forexample with a cycle of 20 ms and a duty ratio of 20%) to the internalswitch module to make the battery group short the circuit in a shorttime. So the heating purpose is achieved. Meanwhile, the battery heatersends a CAN signal to the meter. The meter receives the CAN signal anddisplays that “the battery group is being heated”.

When the battery group is heated, the battery management device and thebattery heater keep on detecting the status of the battery group. If thetemperature of the battery group is higher than the first heatingthreshold, or the continuous heating time is larger than the heatingtime duration threshold, or the maximum temperature of a single batteryin the battery group is higher than the second heating threshold, thebattery heater stops sending the control pulse to the internal switchmodule to stop heating the battery group.

Further, the battery heater sends a CAN signal to the meter. The meterreceives the CAN signal and displays that “the heating is finished”.Thus, the heating procedure is completed. In one embodiment of thepresent disclosure, the second heating threshold may be 20° C., and theheating time threshold may the 20 minutes. Preferably, in order to avoida repeated start of the heating procedure, during the heating process,if the temperature of the battery group is detected to be higher thanthe first heating threshold by 5° C., the battery group is stopped frombeing heated.

If the temperature of the battery group is higher than the first heatingthreshold, the battery management device works normally. If thetemperature of the battery group is lower than the first heatingthreshold and the residual electric quantity of the battery group isless than the parking electric quantity threshold, the primary contactoris not switched on and the battery management device sends the CANsignal to the battery heater and the meter, so that the battery group isnot allowed to be heated. When the meter receives the CAN signal, themeter displays that “the residual electric quantity of the battery groupis not enough” so that the electric vehicle is not allowed to be heated,driven or charged.

If a failure of the battery heater, including under voltage protection,over-voltage protection, overheat protection, pulse width intervalprotection or maximum turn-on time protection, appears during theself-test process, it is not allowed to heat the battery group. Thebattery heater sends a failure signal. The meter receives the failuresignal and displays that “a failure in the battery heater”. The heatingis not allowed.

If any failure of the battery heater, including under voltageprotection, over-voltage protection, overheat protection, pulse widthinterval protection or maximum turn-on time protection, appears duringthe heating process, the battery heater stops heating the battery groupand sends a failure signal. The meter receives the failure signal anddisplays that “a failure in the battery heater”. The heating is ceased.

In some embodiments of the present disclosure, the battery heatercomprises a protection circuit to prevent the failures mentioned above.The protection circuit is described in detail as follows.

(1) When there is a failure signal, an IGBT in the battery heater isturned off. An ERROR (failure) pin of the protection circuit is set at alow level, and a failure signal is outputted through an optical coupler.Thus an ERROUT (failure output) pin is at the low level. To release theprotection status, the PWM (pulse width modulation) wave should bemaintained at a high level for 2 seconds, and then the failure signal isreset and the protection circuit is recovered to a normal status. If thefailure signal cannot be reset by the PWM wave in 2 seconds, a permanenterror occurs in the protection circuit so that the protection circuitcannot work normally.

(2) To ensure a normal work of a discharge module of the IGBT, thefrequency of the pulse sent by a DSP (digital signal processor) may notbe too high and the pulse width may not be too long. For example, amaximum pulse width may be 5 ms and a minimum interval may be 7-10 ms,or else a failure signal may be outputted.

(3) In one embodiment of the present disclosure, a DC-DC isolation powersupply is used to drive the IGBT. The positive bias voltage for the gateterminal of the IGBT may be +15V, and the negative bias voltage for thegate terminal of the IGBT may be −7V. The negative bias voltage for thegate terminal of IGBT may turn off the IGBT quickly and avoid amalfunction of turning on IGBT because of the overlarge surge current.

(4) In one embodiment of the present disclosure, the protection circuitcomprises an under voltage protection circuit. The under voltageprotection circuit may avoid an increase in the power consumption of theIGBT caused by the deficient driving voltage. When the driving voltagedecreases to a first voltage threshold, the under voltage protectioncircuit starts to work. In one embodiment of the present disclosure, thefirst voltage threshold may be 9V.

(5) The over-heat protection circuit may avoid the damage to the IGBTcaused by the high temperature. The protection circuit samples thetemperature by using a thermistor. When the temperature of the IGBT ishigher than a safe temperature threshold, the over-heat protectioncircuit starts to work. The protection circuit may also be configured todetect whether there is an open circuit in the thermistor. When there isan open circuit in the thermistor, the equivalent impedance is infiniteand a protection signal is outputted. In one embodiment of the presentdisclosure, the safe temperature threshold may be 85° C.

(6) Because there is a large inductance in the discharge loop, when theIGBT is turned off, an over-high voltage may be excited by the collectorterminal of the IGBT. So a high voltage capacitor is connected inparallel between the collector terminal and the emitter terminal of theIGBT. The over-voltage protection circuit may avoid the over highvoltage of the collector terminal to damage the IGBT at the moment ofturning off the IGBT. When the voltage of the collector terminal islarger than a second voltage threshold, a protection signal isoutputted. In one embodiment of the present disclosure, the secondvoltage threshold may be 800V.

During the heating process of the battery group, if the user suddenlypresses and holds the heating button for 2 seconds, the battery heaterstops heating the battery group so that the battery group is not allowedto be charged and the electric vehicle is not allowed to be driven.

With the method for heating the battery of the power system of theelectric vehicle according to embodiments of the present disclosure, thebattery group of the electric vehicle may be heated without any externalpower supply. The battery group is heated to a required temperature andthen may be charged or discharged normally. So the restriction on theuse of the electric vehicle at the low temperature may be greatlyreduced and the requirements of running and charging at the lowtemperature may be satisfied. Furthermore, by adjusting the heatingpower of the battery heater according to the real-time temperature ofthe battery group, it is possible to control the heating procedure moreprecisely to make better use of the performance of the battery group andincrease the safety of the battery group.

In the preceding specification, the subject matter has been describedwith reference to specific exemplary embodiments. It will, however, beevident that various modifications and changes may be made withoutdeparting from the spirit and scope of the claimed subject matter as setforth in the claims that follow. The specification and drawings areaccordingly to be regarded as illustrative rather than restrictive.Other embodiments may be apparent to those skilled in the art fromconsideration of the specification and practice of the embodimentsdisclosed herein.

1. A power system of an electric vehicle, comprising: a battery group; abattery heater, connected with the battery group and configured tocharge and discharge the battery group to heat the battery group,wherein the battery heater comprises an output power adjusting moduleconfigured to adjust a heating power of the battery heater by adjustingat least one of a charge current and a discharge current; a batterymanagement device, connected with the battery group and the batteryheater respectively, and configured to control the output poweradjusting module to adjust the heating power of the battery heater toheat the battery group according to a temperature of the battery groupwhen the temperature of the battery group is lower than a first heatingthreshold and a residual electric quantity of the battery group islarger than a parking electric quantity threshold; an electricdistribution box, configured to distribute a voltage output by thebattery group; a motor; a motor controller, connected with the motor andthe electric distribution box respectively, comprising a first inputterminal, a second input terminal and a pre-charging capacitor connectedbetween the first input terminal and the second input terminal, andconfigured to supply power to the motor according to a control commandand a voltage distributed by the electric distribution box; and anisolation inductor, connected between the battery group and the electricdistribution box, wherein an inductance of the isolation inductormatches with a capacitance of the pre-charging capacitor.
 2. The powersystem of claim 1, wherein the battery management device is furtherconfigured to control the electric vehicle to enter into a runningheating mode when the temperature of the battery group is lower than thefirst heating threshold and the residual electric quantity of thebattery group is larger than a running electric quantity threshold, inwhich the running electric quantity threshold is larger than the parkingelectric quantity threshold.
 3. The power system of claim 2, wherein thebattery management device controls the battery heater to heat thebattery group in the running heating mode when any of followingconditions is satisfied: the temperature of the battery group is higherthan a first temperature threshold and lower than a second temperaturethreshold, and the residual electric quantity of the battery group islarger than a first electric quantity threshold; the temperature of thebattery group is higher than the second temperature threshold and lowerthan a third temperature threshold, and the residual electric quantityof the battery group is larger than a second electric quantitythreshold, in which the second electric quantity threshold is lower thanthe first electric quantity threshold; the temperature of the batterygroup is higher than the third temperature threshold and lower than afourth temperature threshold, and the residual electric quantity of thebattery group is larger than a third electric quantity threshold, inwhich the third electric quantity threshold is lower than the secondelectric quantity threshold; and the temperature of the battery group ishigher than the fourth temperature threshold and lower than a fifthtemperature threshold, and the residual electric quantity of the batterygroup is larger than a fourth electric quantity threshold, in which thefourth electric quantity threshold is lower than the third electricquantity threshold.
 4. The power system of claim 2, wherein the batterymanagement device is further configured to: judge whether thetemperature of the battery group is higher than a sixth temperaturethreshold; when the temperature of the battery group is higher than thesixth temperature threshold, judge whether the residual electricquantity of the battery group is larger than a fifth electric quantitythreshold, and when the residual electric quantity of the battery groupis larger than a fifth electric quantity threshold, control the batteryheater to heat the battery group in the running heating mode; when thetemperature of the battery group is lower than the sixth temperaturethreshold, judge whether the temperature of the battery group is higherthan a seventh temperature threshold; when the temperature of thebattery group is higher than the seventh temperature threshold, judgewhether the residual electric quantity of the battery group is largerthan a sixth electric quantity threshold, and when the residual electricquantity of the battery group is larger than a sixth electric quantitythreshold, control the battery heater to heat the battery group in therunning heating mode, in which the sixth electric quantity threshold islarger than the fifth electric quantity threshold; when the temperatureof the battery group is lower than the seventh temperature threshold,judge whether the temperature of the battery group is higher than aneighth temperature threshold; when the temperature of the battery groupis higher than the eighth temperature threshold, judge whether theresidual electric quantity of the battery group is larger than a seventhelectric quantity threshold, and when the residual electric quantity ofthe battery group is larger than a seventh electric quantity threshold,control the battery heater to heat the battery group in the runningheating mode, in which the seventh electric quantity threshold is largerthan the sixth electric quantity threshold; when the temperature of thebattery group is lower than the eighth temperature threshold, judgewhether the temperature of the battery group is higher than a ninthtemperature threshold; and when the temperature of the battery group ishigher than the ninth temperature threshold, judge whether the residualelectric quantity of the battery group is larger than an eighth electricquantity threshold, and when the residual electric quantity of thebattery group is larger than an eighth electric quantity threshold,control the battery heater to heat the battery group in the runningheating mode, in which the eighth electric quantity threshold is largerthan the seventh electric quantity threshold.
 5. The power system ofclaim 2, wherein the battery management device is further configured tocontrol the electric vehicle to enter into a parking heating mode whenthe temperature of the battery group is lower than the first heatingthreshold and the residual electric quantity of the battery group islower than the running electric quantity threshold but larger than theparking electric quantity threshold.
 6. The power system of claim 5,wherein the battery management device controls the battery heater toheat the battery group in the parking heating mode when any of followingconditions is satisfied: the temperature of the battery group is higherthan a tenth temperature threshold and lower than an eleventhtemperature threshold, and the residual electric quantity of the batterygroup is larger than a ninth electric quantity threshold; thetemperature of the battery group is higher than the eleventh temperaturethreshold and lower than a twelfth temperature threshold, and theresidual electric quantity of the battery group is larger than a tenthelectric quantity threshold, in which the tenth electric quantitythreshold is lower than the ninth electric quantity threshold; thetemperature of the battery group is higher than the twelfth temperaturethreshold and lower than a thirteenth temperature threshold, and theresidual electric quantity of the battery group is larger than aneleventh electric quantity threshold, in which the eleventh electricquantity threshold is lower than the tenth electric quantity threshold;and the temperature of the battery group is higher than the thirteenthtemperature threshold and lower than a fourteenth temperature threshold,and the residual electric quantity threshold is larger than a twelfthelectric quantity threshold, in which the twelfth electric quantitythreshold is lower than the eleventh twelfth electric quantitythreshold.
 7. The power system of claim 5, wherein the batterymanagement device is further configured to: judge whether thetemperature of the battery group is higher than a fifteenth temperaturethreshold; when the temperature of the battery group is higher than thefifteenth temperature threshold, judge whether the residual electricquantity of the battery group is larger than a thirteenth electricquantity threshold, and when the residual electric quantity of thebattery group is larger than a thirteenth electric quantity threshold,control the battery heater to heat the battery group in the parkingheating mode; when the temperature of the battery group is lower thanthe fifteenth temperature threshold, judge whether the temperature ofthe battery group is higher than a sixteenth temperature threshold; whenthe temperature of the battery group is higher than the sixteenthtemperature threshold, judge whether the residual electric quantity ofthe battery group is larger than a fourteenth electric quantitythreshold, and when the residual electric quantity of the battery groupis larger than a fourteenth electric quantity threshold, control thebattery heater to heat the battery group in the parking heating mode, inwhich the fourteenth electric quantity threshold is larger than thefifteenth electric quantity threshold; when the temperature of thebattery group is lower than the sixteenth temperature threshold, judgewhether the temperature of the battery group is higher than aseventeenth temperature threshold; when the temperature of the batterygroup is higher than the seventeenth temperature threshold, judgewhether the residual electric quantity of the battery group is largerthan a fifteenth electric quantity threshold, and when the residualelectric quantity of the battery group is larger than a fifteenthelectric quantity threshold, control the battery heater to heat thebattery group in the parking heating mode, in which the fifteenthelectric quantity threshold is larger than the fourteenth electricquantity threshold; when the temperature of the battery group is lowerthan the seventeenth temperature threshold, judge whether thetemperature of the battery group is higher than an eighteenthtemperature threshold; when the temperature of the battery group ishigher than the eighteenth temperature threshold, judge whether theresidual electric quantity of the battery group is larger than asixteenth electric quantity threshold, and when the residual electricquantity of the battery group is larger than a sixteenth electricquantity threshold, control the battery heater to heat the battery groupin the parking heating mode, in which the sixteenth electric quantitythreshold is larger than the fifteenth electric quantity threshold. 8.The power system of claim 1, wherein: when the temperature of thebattery group is higher than a third heating threshold and lower than afourth heating threshold, the battery management device controls thebattery heater to heat the battery group with a first power, when thetemperature of the battery group is higher than the fourth heatingthreshold and lower than a fifth heating threshold, the batterymanagement device controls the battery heater to heat the battery groupwith a second power, in which the second power is lower than the firstpower; when the temperature of the battery group is higher than thefifth heating threshold and lower than a sixth heating threshold, thebattery management device controls the battery heater to heat thebattery group with a third power, in which the third power is lower thanthe second power; and when the temperature of the battery group ishigher than the sixth heating threshold and lower than a seventh heatingthreshold, the battery management device controls the battery heater toheat the battery group with a fourth power, in which the fourth power islower than the third power.
 9. The power system of claim 1, wherein thebattery heater further comprises: a first switch module, a firstterminal of the first switch module connected with a first electrode ofthe battery group and the isolation inductor respectively; at least onefirst capacitor, wherein a first terminal of the at least one firstcapacitor is connected with a second terminal of the first switchmodule, and a second terminal of the at least one first capacitor isconnected with a second electrode of the battery group; a firstinductor, wherein a first terminal of the first inductor is connectedwith a node between the first switch module and the at least one firstcapacitor, and a second switch module, wherein a first terminal of thesecond switch module is connected with a second terminal of the firstinductor, and a second terminal of the second switch module is connectedwith the second electrode of the battery group, wherein a controlterminal of the first switch module and a control terminal of the secondswitch module are connected with the battery management device, and thebattery management device sends a heating signal to the control terminalof the first switch module and the control terminal of the second switchmodule to control the first switch module and the second switch moduleto turn on in turn so as to generate the charge current and thedischarge current in turn, in which the first switch module is on whenthe second switch module is off, and the first switch module is off whenthe second switch module is on.
 10. The power system of claim 9, whereinthe output power adjusting module is further configured to adjust dutyratios of output pulses of the first switch module and the second switchmodule according to a first instruction sent by the battery managementdevice.
 11. The power system of claim 9, wherein the battery heatercomprises a plurality of first capacitors, and the output poweradjusting module is further configured to adjust a number of operationalcapacitors of the plurality of first capacitors according to a secondinstruction sent by the battery management device.
 12. The power systemof claim 1, further comprising a relay.
 13. The power system of claim 1,wherein the electric distribution box comprises: a primary contactor,configured to distribute the voltage output by the battery group to apower consumption equipment of the electric vehicle; and apre-charging-contactor, connected with the first input terminal or thesecond input terminal of the motor controller, and configured to chargethe pre-charging capacitor under a control of the battery managementdevice before the motor controller controls the motor to start.
 14. Anelectric vehicle comprising a power system of claim 1
 15. A method forheating a battery group of an electric vehicle, comprising: detecting atemperature and a residual electric quantity of the battery group; whenthe temperature of the battery group is lower than a first heatingthreshold and the residual electric quantity of the battery group islarger than a parking electric quantity threshold, adjusting a heatingpower of a battery heater to heat the battery group according to thetemperature of the battery group; and when the temperature of thebattery group is lower than the first heating threshold and the residualelectric quantity of the battery group is lower than the parkingelectric quantity threshold, indicating that the battery group isinhibited from being heated or charged and the electric vehicle isinhibited from being driven.
 16. The method of claim 15, furthercomprising: controlling the electric vehicle to enter into in a runningheating mode when the temperature of the battery group is lower than thefirst heating threshold and the residual electric quantity of thebattery group is larger than a running electric quantity threshold, inwhich the running electric quantity threshold is larger than the parkingelectric quantity threshold.
 17. The method of claim 16, furthercomprising: controlling the battery heater to heat the battery group inthe running heating mode; wherein the step of controlling the batteryheater to heat the battery group in the running heating mode isperformed when any of following conditions is satisfied: the temperatureof the battery group is higher than a first temperature threshold andlower than a second temperature threshold, and the residual electricquantity of the battery group is larger than a first electric quantitythreshold; the temperature of the battery group is higher than thesecond temperature threshold and lower than a third temperaturethreshold, and the residual electric quantity of the battery group islarger than a second electric quantity threshold, in which the secondelectric quantity threshold is lower than the first electric quantitythreshold; the temperature of the battery group is higher than the thirdtemperature threshold and lower than a fourth temperature threshold, andthe residual electric quantity of the battery group is larger than athird electric quantity threshold, in which the third electric quantitythreshold is lower than the second electric quantity threshold; and thetemperature of the battery group is higher than the fourth temperaturethreshold and lower than a fifth temperature threshold, and the residualelectric quantity of the battery group is larger than a fourth electricquantity threshold, in which the fourth electric quantity threshold islower than the third electric quantity threshold.
 18. The method ofclaim 16, wherein controlling the battery heater to heat the batterygroup in the running heating mode comprises: judging whether thetemperature of the battery group is higher than a sixth temperaturethreshold; when the temperature of the battery group is higher than thesixth temperature threshold, judging whether the residual electricquantity of the battery group is larger than a fifth electric quantitythreshold, and when the residual electric quantity of the battery groupis larger than a fifth electric quantity threshold, controlling thebattery heater to heat the battery group in the running heating mode;when the temperature of the battery group is lower than the sixthtemperature threshold, judging whether the temperature of the batterygroup is higher than a seventh temperature threshold; when thetemperature of the battery group is higher than the seventh temperaturethreshold, judging whether the residual electric quantity of the batterygroup is larger than a sixth electric quantity threshold, and when theresidual electric quantity of the battery group is larger than a sixthelectric quantity threshold, controlling the battery heater to heat thebattery group in the running heating mode, in which the sixth electricquantity threshold is larger than the fifth electric quantity threshold;when the temperature of the battery group is lower than the seventhtemperature threshold, judging whether the temperature of the batterygroup is higher than an eighth temperature threshold; when thetemperature of the battery group is higher than the eighth temperaturethreshold, judging whether the residual electric quantity of the batterygroup is larger than a seventh electric quantity threshold, and when theresidual electric quantity of the battery group is larger than a seventhelectric quantity threshold, controlling the battery heater to heat thebattery group in a running heating mode, in which the seventh electricquantity threshold is larger than the sixth electric quantity threshold;when the temperature of the battery group is lower than the eighthtemperature threshold, judging whether the temperature of the batterygroup is higher than a ninth temperature threshold; and when thetemperature of the battery group is higher than the ninth temperaturethreshold, judging whether the residual electric quantity of the batterygroup is larger than an eighth electric quantity threshold, and when theresidual electric quantity of the battery group is larger than an eighthelectric quantity threshold, controlling the battery heater to heat thebattery group, in which the eighth electric quantity threshold is largerthan the seventh electric quantity threshold.
 19. The method of claim16, further comprising: controlling the electric vehicle to enter into aparking heating mode when the temperature of the battery group is lowerthan the first heating threshold and the residual electric quantity ofthe battery group is lower than the running electric quantity thresholdbut larger than the parking electric quantity threshold.
 20. The methodof claim 19, further comprising: controlling the battery heater to heatthe battery group in the parking heating mode; wherein the step ofcontrolling the battery heater to heat the battery group in a parkingheating mode is performed when any of following conditions is satisfied:the temperature of the battery group is higher than a tenth temperaturethreshold and lower than an eleventh temperature threshold, and theresidual electric quantity of the battery group is larger than a ninthelectric quantity threshold; the temperature of the battery group ishigher than the eleventh temperature threshold and lower than a twelfthtemperature threshold, and the residual electric quantity of the batterygroup is larger than a tenth electric quantity threshold, in which thetenth electric quantity threshold is lower than the ninth electricquantity threshold; the temperature of the battery group is higher thanthe twelfth temperature threshold and lower than a thirteenthtemperature threshold, and the residual electric quantity of the batterygroup is larger than an eleventh electric quantity threshold, in whichthe eleventh electric quantity threshold is lower than the tenthelectric quantity threshold; and the temperature of the battery group ishigher than the thirteenth temperature threshold and lower than afourteenth temperature threshold, and the residual electric quantitythreshold is larger than a twelfth electric quantity threshold, in whichthe twelfth electric quantity threshold is lower than the eleventhtwelfth electric quantity threshold.
 21. The method of claim 19, whereincontrolling the battery heater to heat the battery group in the parkingheating mode comprises: judging whether the temperature of the batterygroup is higher than a fifteenth temperature threshold; when thetemperature of the battery group is higher than the fifteenthtemperature threshold, judging whether the residual electric quantity ofthe battery group is larger than a thirteenth electric quantitythreshold, and when the residual electric quantity of the battery groupis larger than a thirteenth electric quantity threshold, controlling thebattery heater to heat the battery group in the parking heating mode;when the temperature of the battery group is lower than the fifteenthtemperature threshold, judging whether the temperature of the batterygroup is higher than a sixteenth temperature threshold; when thetemperature of the battery group is higher than the sixteenthtemperature threshold, judging whether the residual electric quantity ofthe battery group is larger than a fourteenth electric quantitythreshold, and when the residual electric quantity of the battery groupis larger than a fourteenth electric quantity threshold, controlling thebattery heater to heat the battery group in the parking heating mode, inwhich the fourteenth electric quantity threshold is larger than thethirteenth electric quantity threshold; when the temperature of thebattery group is lower than the sixteenth temperature threshold, judgingwhether the temperature of the battery group is higher than aseventeenth temperature threshold; when the temperature of the batterygroup is higher than the seventeenth temperature threshold, judgingwhether the residual electric quantity of the battery group is largerthan a fifteenth electric quantity threshold and when the residualelectric quantity of the battery group is larger than a fifteenthelectric quantity threshold, controlling the battery heater to heat thebattery group in the parking heating mode, in which the fifteenthelectric quantity threshold is larger than the fourteenth electricquantity threshold; when the temperature of the battery group is lowerthan the seventeenth temperature threshold, judging whether thetemperature of the battery group is higher than an eighteenthtemperature threshold; when the temperature of the battery group ishigher than the eighteenth temperature threshold, judging whether theresidual electric quantity of the battery group is larger than asixteenth electric quantity threshold, and when the residual electricquantity of the battery group is larger than a sixteenth electricquantity threshold, controlling the battery heater to heat the batterygroup in the parking heating mode, in which the sixteenth electricquantity threshold is larger than the fifteenth electric quantitythreshold.
 22. The method of claim 15, wherein adjusting a heating powerof a battery heater to heat the battery group according to thetemperature of the battery group comprises: when the temperature of thebattery group is larger than a third heating threshold and lower than afourth heating threshold, controlling the battery heater to heat thebattery group with a first power; when the temperature of the batterygroup is larger than a fourth heating threshold and lower than a fifthheating threshold, controlling the battery heater to heat the batterygroup with a second power, in which the second power is lower than thefirst power; when the temperature of the battery group is larger than afifth heating threshold and lower than a sixth heating threshold,controlling the battery heater to heat the battery group with a thirdpower, in which the third power is lower than the second power; and whenthe temperature of the battery group is larger than a sixth heatingthreshold and lower than a seventh heating threshold, controlling thebattery heater to heat the battery group with a fourth power, the fourthpower is lower than the third power.
 23. The method of claim 15, furthercomprising: calculating a current temperature of the battery group and acurrent residual electric quantity of the battery group; calculating amaximum output power of the battery group according to the currenttemperature of the battery group and the current residual electricquantity of the battery group; and controlling the electric vehicle torun under a limited power according to the maximum output power of thebattery group.
 24. The method of claim 15, further comprising:controlling the battery heater to stop heating the battery group whenany of following conditions is satisfied: the temperature of the batterygroup is higher than the first heating threshold; a temperature of anysingle battery in the battery group is higher than a second heatingthreshold, wherein the second heating threshold is larger than the firstheating threshold; and a continuous heating time of the battery heateris larger than a heating time threshold.